Patent GB-859504-A (GB)
Title: Improvements relating to a mechanism for deflecting a control surface of an aircraft
Inventor: FOWLER JOHN LAWRENCE
IPC: B64C13/24
Filed: 1956-05-09
Abstract: 859,504. Controlling aircraft. FAIREY CO. Ltd. Aug. 9, 1957 [May 9, 1956], No. 14395/ 56. Class 4. [Also in Group XXIX] In a hydraulic servomotor control system for operating an aircraft control surface, comprising a servomotor, a control valve therefor and a control mechanism coupled to the valve to cause it to operate the servomtoror in response to either movement of a manual control member, an automatically generated signal representing a desired control surface movement or the operation of a manual or automatic trim setting member, the parts of the system are assembled as a self-contained unit. The unit 80, Fig. 2, comprises a casting 81 housing respectively servo, trim-setting and " feel " control valves 13, 35, 58 and an inlet manifold 16 supplying the valves from either of two independent liquid pressure sources. The unit also includes a trimming jack 30, a servomotor 10 connected, e.g. to the aircraft elevators, and stabilizer, trimming and " feel " electric motors 27, 39, 59 operatively connected to the valves 13, 35, 58 respectively. A circular " feel " spring 50 is fixed at one end 51, and connected at its other end to a " feel " jack (not shown). Input and output levers 32, 20 connected by rods 18, 11 to the pilot's control column and the elevator respectively complete the unit. As shown in the schematic diagram, Fig. 1, under manual control, movement of the control column 17 rotates the levers 32, 20 about their ends 31, 24 connected to the trimming jack 30 and the servomotor 10 respectively. A floating lever 21 pivotally mounted on the lever 20 and connected at its ends 25, 26 to the valve 13 and the electric stabilizer motor 27 respectively rotates about its end 26 to operate the valve 13 and hence the servomotor 10 to adjust the elevator 12. With the aircraft under automatic control, any deviation from control surface setting is detected by an auto-stabilizer 28 which receives signals derived from the gyroscope of the automatic pilot and feeds them to the stabilizer motor 27 which through the lever 21 again operates the valve 13 and servomotor 10. Under trim control the pilot presses a button 40 which through a potentiometer 41 excites the motor 39 to operate the valve 35 and so move the trimming jack 30 to rotate the lever 32 about a point 54 connected to the free end of the spring 50. This will produce corresponding movement of the elevator in the same way as when moved by the control column, the control column taking up a new position. The " feel " motor 59 is actuated by electric signals derived from the air speed indicator (AS1), Machmeter (M) and accelerometer (A) in accordance with actual flight conditions and operates the valve 58 which in turn moves the jack 57 and through a rack and pinion sector rotates an arm 55 to vary the stiffness of the spring 50 which variation is transmitted to the pilot through the lever 32, link 18 and column 17, to provide artificial " feel ". The valve 58 is provided with " failsafe " means comprising a solenoid-actuated valve 60 controlled in an emergency by a button on the control column 17 to reverse the flow through the valve 58 to the jack 57 so that the " feel " is instantly reduced. Potentiometers fitted on the servomotor 10 and the jacks 30, 57 provide feed-back signals to the motors 27, 39, 59 to stop these motors when the servomotor and jacks reach their desired new settings. The servomotor 10 instead of being connected directly to the elevator may be connected thereto through a further control valve and a larger serovmotor 10A. Specification 814,291 is referred to.